View Full Version : Big Turbo and High Performace 1.8T guide..

02-24-2009, 05:01 PM
TAKEN FROM http://www.audifreaks.com/showthread.php?t=26


I thought this was a good read, and instead of just pasting a stupid link somewhere I thought I would bring it over..

This thread is to cover the basics and what is needed to go BT and other high performance parts.


First, for anyone not sure how turbos or turbo cars work,please go here and read first. (http://www.howstuffworks.com/turbo.htm)


Please read the following info from garrett
GARRETT turbo tech 101 (http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech101.html)
GARRETT turbo tech 102 (http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech102.html)
GARRETT turbo tech 103 (http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.htm)

Please get very familure with mainly 101 and 102. 103 is more advanced than most will need to be. But if you can understand 102, you are ahead of the curve and will be able to handle turbo talk on the forums.


The 1.8t came built extremely strong. The block itself doesnt need sleeved like in other brands engines. The pistons are forged and made by Mahle and have seen over 700hp on an engine dyno. The cranks are forged also and have yet to break due to power. The only week part of the engine is the rods. They are good for 310-330wtq depending on 19mm or 20mm wrist pins and turbo used.

Basically to make big power on a 1.8t, you basically only need to swap rods with aftermarket H-beam or X-beam rods. This will allow you to make over 500whp depending on turbo and other mods.

AEB/ATC/AMU/BEA rods - SCAT H beam - PAUTER X beam


To properly size a turbo, you need to have some idea on what your goals are and how much work you plan on doing. Do you want a fast spooling turbo? Do you want to change rods? ETC.


KO3(S) - 200-220WHP 230-250WTQ
KO4-001 - 220-240WHP 240-280WTQ
KO4-20/22/23 - 230-260WHP 200-220AWHP 260-300WTQ

These are more of a tq producing turbo. Great for low end power (2500-6000rpms), but they suffer major power drop off at 5500-6k rpms.


GT turbos are DBB (dual ball bearing) if they end with a R. If not, they are journal bearings and have gt style wheels. DBB turbosspool up 15% faster and consume less than 1/2 the power than journal bearings turbos. This means faster spools ups and more over all power than journal bearing turbos.

As you should of learned in TURBO TECH 102, all GT turbos are put in families (GT25, GT28, GT30 etc aka shared turbine wheels) and the last 2 numbers are the size of the exducers.


TURBO NAME - POWER LEVEL - EXPECTED SPOOL (based on most popular housings).

GT28R /GT2560R - 270-300whp - 3000rpms
GT28RS /GT2860R - 290-330whp - 3200rpms
*GT2871R -325-360whp - ~3400rpms
*GT3071R - 360-425WHP - ~3800rpms
*GT3076R - 380 - 500whp - ~3900rpms**
*GT3082R/GT3040R - 440-550whp - ~4200rpms**
*GT35R/GT3582R/GT3540R - 450-600whp - ~4700rpms**

All housings are based on .64 T25 housings for the GT28 family and .63 T3 housing for GT30/GT35 turbos. These work out for the fastest spool with the good flow.

* Denotes that to use these turbos to their full potential you will need to do rods so you dont blow your engine. Also you will start to see significant gains by changing out other parts like intake manifolds, cams, and either port or move to a AEM big port head.

** Denotes turbos would also benifit from an increase in housing to .82 T3. Expect 500rpm increase for an increase in housing size. You will however increase the top end greatly at the sacrifice of some low end power.


These turbos are all journal/thrust bearing turbos unless the chra (center cartrage) is changed to aDBB unit. They are often just oil cooled unless again, upgraded. You can also get the T series turbo in two versions, 270 or 360 thrust bearings. The 360's oil far better and since the T series turbos use more oil, it is a good idea to get the $50 upgrade. If it doesnt say 360, it is a 270 thrust bearing. Pagparts.com is the only place off the top of my head that i know of that sells both. As stated before, journal bearings spool slower which isnt always a negative. A t3t4 turbo can make more power on the stock rods than a faster spooling GT turbo. Not to mention that since they use older tech, they are about 1/2 the cost of a GT turbo. You can however decrease lag on a T series with a smaller housing (using a .48 instead of a .63).

T3s60 - 270-310whp - 3100rpms
T3T4 50trim .48 - 300-375whp - ~3800rpms
T3T4 50trim .63 - 300-400whp - ~4200rpms
T3T4 57trim - not a very efficient turbo, surges above 20psi. Avoid use.
T3T4 60trim - .63 - 320-425whp - ~4400rpms
T3/GT40 - .63 - 375-600whp ~4600rpms (GT35/40 82mm wheel with stg 3 turbine wheel)
SC61 - .63 - 375-600whp ~4800rpms (GT35/40 82mm wheel with ptrim turbine wheel)
stage 1 ( 1.916 / 2.320 )
stage 2 ( 2.120 / 2.555 )
stage 3 ( 2.227 / 2.555 )
stage 4 ( ????? / ????? )
stage 5 ( 2.437 / 2.795 )

Same applies as above, to max out these turbo, you will need to rods. Also when you choose, you can upgrade the chra to a DBB unit and have faster spool and higher power potential. Take into account, if you were using a .48 housing, you need to swap to a .63 housing with it also.


These turbos are journal bearings which spool like a dbb turbo. The reason for this is the ETT (extended tip technology). Simply put, its a taller, more efficient blade design which both improves spool ups and gives the turbo a HUGE efficiency island compared to a GT turbo and even more vs a T series. These turbos also use a much larger wheels than those on GT turbos which help reduce backpressure for even more flow and they are attached to a much thicker shaft than a GT turbo. The best part of these turbos is that they are completely rebuildable unlike a GT turbo where you are out atleast $600 for chra replacement or more for a completely new chra. The only downside to these turbos is that they are larger in size which adds weight (3-6lbs vs a gt turbo) and are only oil cooled.

S256 - 350-500whp - ~4200rpms
S258 - 350-550whp - ~4400rpms
S362 - 400-600+whp - ~4700rpms

There are others, but these are the 3 most popular. Also they come in a BW housing or a Bullseye Power SS housing in .55 and .70 housings. Theses are growing in popularity and deff a great turbo


These turbos can either be bought from FP or they can rebuild your current GT3076r or GT3582r. They remove the garrett wheel and add in there lighter billet 7 blade compressor wheel that mimics the BW ETT. These wheels will cut off a few hundred rpms of lag while increasing the lb/min rating. They recommend that you use the larger .82 housing with all versions but a .63 on a 1.8T will still be good.

HTA3076r - increases the lb/min from 54lb/min to over 57lb/min. This is good for over 30whp and 200-400rpms less lag
HTA3582r - No lb/min given but has a dramatic increase in mid range power and keeps the power increase till redline. Good for another 30-50whp in those areas
HTA3586r - This is the largest exducer that can fit in the T3 covers. Over 700awhp has been made with this turbo on evos and is most likely beyond what most will need.


These are modified GT turbos with a ko3/4 style housings. They are a great concept but the problem with these turbos is that the flange is a huge restriction on flow. Also the housing style doesnt flow well enough for a high hp turbo. The GT2X and GT28R will be fine using a upgraded manifold and have reasonable spool. The GTRS and GT71R have a rather large increase in lag and lower power output compared to the T25 manifold and housing. Also it sounds like its a cost savings but in the end, it cost close to the same a whole kit. If money is an issue, a T series kit would be a better option.

GT2X- 240-250whp stock like spool with more psi held till redline
GT28R - 260-280whp - ~3300rpms
GTRS - 280-300whp - ~3600rpms
GT71R -290-320whp - ~3900rpms

Obviously there are 1000's of turbos and varients out there, these are just the most popular and have great tuning and parts to go with them

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02-24-2009, 05:01 PM

Each manifold needs to match the turbine housing used. You cant run a T25 or T3 turbo on the other manifold and definitely not the stock manifold.

Manifolds are madein two styles.

CAST: These manifolds are made of cast iron and are used for their durabilitly and ability to handle the heat cycles (heat up and down) over and over. These manifolds will most often outlast the car if they are made well. However, they are very heavy and often timestrade flow for turbo placement. For best results, make sure the runners do not fire against each other and wastegate placement is close to the flange.

TUBULAR: These manifolds are made out of mild or stainless steel. They can be either very strong or very weak depending on the materials used and howthey werewelded. When it comes to these types of manifolds, you often get what you pay for. A cheap eBay manifold will often crack withen a short period of time after install and should never be used. Please use repitable brands such as FULL-RACE and 034motorsports. They both are made with the finest materials and F-R uses robotic welding to insure a perfect weld. It is also advised to support the turbo to prevent cracking of the manifold.F-R manifoldsalso come with a lifetime warrenty. The biggest benifits of these manifoldsare they flow far better and make a huge increase in power with a larger frame turbo (gt30+). But they do sacrafice a little low end power and increase lag a couple 100rpms.

Bobqzzi's Full Race / ATP Comparrison Dynos

Compressor 76.2mm, 56 Trim .60 ar
Turbine 60mm, 84 Trim, .82 a/r
AER Stadalone Management (England)
Both Pulls @ 23.5 psi
Superflow Engine Dyno

Full Race
hp - red
tq - teal

hp - blue
tq - green


Not a widely used item on the 1.8T. Twin scroll creates two exhaust paths instead of one, allowing for increased separation in exhaust flow. This means the manifold needs to have the cyls paired in firing order for best results so there is a constant flow over the turbine wheel instead of a build up of gas. This also helps to preserve the exhaust velocity of each pulse by offering a smaller overall volume to hold each one, so the turbine wheel will spin easier with a lower amount of gas volume compared to a single scroll. This means faster spool ups on larger wheels/turbos on a smaller displacement motor. For best results the manifold needs to be paired and tuned in length and 2 wastegates to vent the exhaust flow so it will cost more and consume more space.


Just like the manifolds above, the downpipes must match the turbine housing used and also the manifold used. They are not a mix and match part. You will want atleast a 3" dp and made of either a stainless or mild steel. V-bands make the removal/install of the dp far easier.


All turbos will need new oil lines and if the turbo has water lines, it is advised to use them (see turbo tech 101 again). To start, the block will need a new fitting to go from a banjo bolt to a -4an fitting. Then a 4ft -4an line to a restrictor in the turbo. The return needs the return fittingor tapped for a -10 line or larger. Then you can either modify the stock hardpipe or buy a atp pan adapter. Coolent lines are easier, you need the matching banjo bolts and line.


Self explanitory. Just make sure you use a intake that will exceed the flow of the turbo.


Some gaskets are a good idea and insome locations they can be eliminatedto cut the risk of blowing them out and having an exhaust leak

Use gaskets: head -manifold

Dont use gaskets: manfold-> turbo, turbo - dp, external wastegate - manifold


A turbo will either come with a internal wastegate or require an external one. If the turbo requires an external, you will need to have a manifold that comes withflange built in. Then you will also have to use the same size wastegate used since the fittings are differnt. What people dont often understand, is that bigger isnt always needed when it comes to wastegates. The higher the boost used,the smaller the wastegate can be. Since you are using about all of the psi the turbo is capable of making, the wastegate doesnt have much to vent. Since most 1.8t's will boost ~20psi give or take, a internal and 38mm or 44mm for very large turbos will be fine.


NOT ALL CORES ARE EQUAL!! When it comes to ic's, you really do get what you pay for. Sure an eBay core will cool the temps down, but not nearly as well as a name brand core. This loses power 2 ways. First is by having higher iat's (cooler air is denser) and the other by having timing pulled do to the higher iat's. You want a core that is matched for the amount of power you are running. A core that is to small wont cool enough and a core to large will cause pressure drop. Same goes for piping, proper sizing is needed to reduce lag and pressure drop. The rule of thumb is to use the turbo outlet size either all the way around or to the ic and then .25" increase to the TB. It depends more on the size of turbo used and TB size.


These become a must for those looking to make big power. It is recommend that people install rods with gt2871r turbos and larger. If you dont, you are on risking blowing your engine and will sooner than later. What rods you need are based on the engine code you have or piston you plan on using if you change pistons also (for c/r and/or bore). The ATC/AMU/BEA engines all use 144/20mm (length/pin size) rods. The most popular of these are Scat H-beam rods. They are strong enough to hold around 600whp+ (no deffinate power set yet) and are affordable. For those with AWP engine, youneed 144/19mm H-beam rods, Integrated Engineering (IE) makes drop in rods for you. The 19mm wrist pinrods however will put more strain on the bearings and due to the taper design make them a little weaker than the 20mm wrist pin rods. Plenty strong for those looking for up to and over 500whp. Of course there are stronger and nicer x-beam rods from Carrillo and Pauter, but at 3x the price of scats/IE, they are only really needed for those looking for very large numbers.


Not really a must, but when you start going with larger turbos, its a good idea to increase bore size and consider dropping the c/r. The increase in bore will help spool the turbo faster and also help increase base hp (means more power throughout the powerband). With the lowering of the c/r, you can also increase the psi used on pump and increase timing some. However, this does lower base hp and off turbo response. So it is a trade off but does make it safer to tune.


This is just as important as the the hardware. If you cheap out on the sw you will suffer in performance and possibly risk harm to the turbo and engine. Please go with a tune from a repitable chip tuner. The main tuners are again Unitronic, Eurodyne/Tapp, Revo, and Giac (APR of course, but only sold in the kits). Also you must go with a file that uses injectors that are a good match for the turbo used and all the parts required for that tune (ie: MAF, injectors, fpr).

popular file sizes


For those wanting something not off the self can invest in a stand alone engine management system. These sem's either replace or use factory sensors and takes control of running the engine from the ecu. They are perfect for those using a nontypical turbo or going bigger than what the chip tunes have reached yet. However you will need a capable tuner to tune the car and also pay for plenty of dyno time to get it right. With all of this, the cost adds up fast so its not for everyone.



With the upgrade in power you will need to change out stock fueling. The stock injectors will be maxed out with the stock turbo. Depending on what turbo, power levels, and tune you go with will determine the injectors used.

Good guide to sizing:

440cc: 330whp
580cc: 380whp
630cc: 430whp
750cc: 500whp
870cc: 600whp

Also you will need high impedance, wide angle spray pattern injectors. If not, your idle and fuel mixture will be bad. Please stick with genisis and siemas deka injectors. RC's also seem to work well on the 1.8t. Please avoid the 440cc greentops, they cause a bad idle and dont match the factory spray pattern.


You will also need to add in a inline fuel pump. For 500hp (not whp) cars, a walbro 255lph inline pump will be plenty. For those looking for more, a bosch 044 pump will support around 700hp. There is a problem with most aftermarket intake pumps, they often starve for gas when the tank is less than 1/4 tank. So its best and cheapest to just add in a inline pump. Also keep in mind that after you get to around 500whp, you will also be forced to increase the size of the fuel line and also even do a surge tank so you dont starve for fuel.


In most tunes, the stock 3 bar will be used. However, if you do use a differnt size injectors (550cc @4bar = 630cc) or reach the limit of the current injectors, you can increase fuel pressure to increase the cc rating. A adjustable fpr would also be a good idea to help maximize a tune along with unisettings.

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02-24-2009, 05:04 PM

Once you have a larger turbo up and running and the engine is able to hold the power (rods +), you can now max out the turbo. It is HIGHLY recommend that you do not go with these steps on stock rods or with a smaller turbo. Either they will increase torque enough to snap rods or just not be helpful with a smaller turbo uppgrade unless otherwise noted.


This a great thing to use to extract the most power out of your car. The higher octane will allow you to increase the psi and/or timing (some turbos are maxed out on 20-24psi or so). The higher the octane the better. Just make sure to avoid leaded gas. If you do use leaded gas you can clog the cat (if using one) and destroy o2 sensors. People have gotten away with using it and others needed to replace the above after one tank.

This will work with all turbos but not recommended on turbos larger than a gt28rs unless you have rods. Even with a gt28r/t3s60/gt28rs, you can blow a rods if you have a big tq/boost spike. Please use with caution.


This has close to the same benifets as race gas but also lowers the iat's in the process (plus cleans the cylinders). How it works is the water removes the heat from the charged air and adds densitywhile the meth reduces knock and increases octane rating. With this you can now increase boost and timing within reason. It is important to log the cars sensors when tuning with w/m.

For best results a dual nozzle system should be used. For this you would put one large nozzle just post ic anda second smaller nozzle just before or after the TB. The way this works is the further away from the TB the more cooling power it has and the closer to the TB the more knock pretection it has. If you plan on using a single nozzle, it should be placed in between the TB andIC depending on which benifit you desire most. The controller allows you to maximize the sprays potential by adding a smaller amount with lower boost and then spraying full nozzle when the boost peaks. This will keep you from injecting to much or to little w/m at any given boost

This will also work with all turbos but should be use with restraint on boost and timing with larger turbos and stock rods.


With the increase in flow from a larger turbo, the head flow in and out will also make a significant increase. The best way to accomplish this is with a AEB (97-99.5 A4/passat) head. It uses a large port design which is considerably larger than the small port in all other US 1.8t models (see pic below). The large port head is larger on both the intake and exhaust size and continues on down the runners. However, the AEB head does not come with SAI and the head will need machined if you choose to keep it. All parts between the 2 heads are interchangeble. Meaning if you have a bare AEB head, you can swap cams, valves and everything else. Also if you have a VVT car, you can swap over the VVT tensioner or use a nonVVT tensioner and have VVT disabled. There is plenty of info on this swap in the 1.8t section on vwvortex.

If you choose, you can also porta small port head toAEB port size. This will increase flow but not as much as a true AEB head unless the runners are increase also. The runners on the AEB head are wider than the small ports and some welding is required to match the runner sizes.

With either route, you WILL need a large port intake manifold or atleast a transition spacer from 034motorsport. Without the correct head or spacer, you will have turbulance and loss power.




Top is a big port AEB head and the bottom a small port head. You can see the AEB is larger from inlet to the combustion chamber and still has material to be removed for larger ports/runners. This is why the flow so much more than a stock small port head. Also you can see on the small port head that there is a lip to increase velocity of the flow which helps lower hp applications, ie stock turbos.


With or without the increase in port size, a BT car will see a significant gain from losing the stock head for a free flowing head. You can get some in either large or small port and either side TB and even larger TB. Please take all into account when making your decision.

good thread for more info. (http://forums.vwvortex.com/zerothread?id=3098525)



With the increase in turbos of atleast a gt30 series you will also see a nice increase with cams. How much will depend on the grind and other parts used. Cams are not going to gain much of anything unless tuned for. You will have to notify your chip tuner to see if they have a file or can tune for the cams. Most companies either have a mild or aggresive cam and some have a mid grind also. Depending on the power and ride quality you want should help you determine your set. By installing the most aggressive cams will not make a very streetable car. Please select cams with caution.




Another good way to get power is by adding nitrous. It can either be safe or dangerous depending on how it is used and how much. First you will need either a wet or direct port kit. These are the best and safest way to add hp. You can use it with a stock turbo and rods if done with restraint. A 50-75shot is fine if it is injected past peak torque. To be safe, injecting 4k and above will be safe. If injected before, you will have a massive tq spike and put a large hole in the block. However, when you start increasing pressure with psi, you are doing the same with nitrous. Without care, you can build to much pressure in the chamber and break either rods, pistonsor the wrist pins. Again, use with caution.


02-24-2009, 05:05 PM

A great way to fight lag or add more base hp to the motor is increasing the displacement of the motor. There is a couple routes you can take to accomplish this and will be covered below. As for power, my personal car went from rated at 180bhp and 170tq at 11psi to 172whp and 185wtq with only 8psi. That is roughly a gain of 20whp and 40wtq with 3psi less boost using 15% drivetrain loss. This is also with .25 lower in compression and a 3" dp tapered to 2.25 (should negate the decrease in boost).


With using the stock 86.4mm crank, increasing bore size will give you the following:

81mm bore = 1781cc- stock displacement
81.5mm bore = 1801cc
82mm bore = 1825cc
82.5mm bore = 1847 (small 1.9L)
83mm bore = 1870cc (1.9)
83.5mm bore = 1892cc

With using a 2.0T FSI or 2.0 AEG 92.8mm crank will give you the following:

81mm bore = 1912
81.5mm = 1936
82mm = 1960
82.5mm = 1984
83mm = 2008
83.5mm = 2032

It is recommended that you do not go above 83mm on a street car. This gives you enough cyl wall to be strong and not risk blowing the block due to cyl pressure when running large amounts of boost.


the FSI cranks are forged and the AEG crank is cast. There has been much debate over the strength of the cast AEG crank but it has seen well over 500whp and has yet been broken with power. The FSI crank can be found from a couple websites or in a full kit from qedpower.com along with stroker pistons, scat rods,and all the hardware for install. You can find used AEG cranks for <$250 and a new FSI crank is ~$600. You will also need to stock 1.8t oil pump gear installed onto the new crank before it is installed.


You will need a custom set of "stroker" pistons when using a 92.8mm crank. These pistons have the pin (where it attaches to the rod) moved up the 6.4mm to account for the added stroke of the crank all while keeping the stock 144mm length rods. Also all these pistons come with 20mm wrist pins so 144/20mm rods from scat or IE will be needed.

You will also need to take into account the compression ratio (c/r) when ordering the pistons. Keeping the stock 9-9.5:1 is ideal for the street. This keeps plenty of power when not in boost and helps spool the turbo faster all while still being safe to run plenty of boost on pump gas. You can also choose to decrease the compression all the way down to 8-8.5:1. Bringing it down this low will allow you to run more boost on pump and also prevent timing pull. It is also safer on the motor since it decreases cly pressure considerably. This however will make running the car off boost more sluggish. This method is more for the racer (either road or drag) that will be basically in boost the entire time driving the car. Finally you can also increase the c/r. This is a less commonly done since it decreases the amount of boost on pump and makes tuning more important. It will however increase off boost response and spool up which is the plus. The highest that i have seen used is 10:1 which is about the highest one should really use on a F/I car.

When ordering your pistons you can also have the top and skirt coated. This ispretty inexpensive and offer good benefits.Having the top coated will help reduceknock and prevent some timing pull. Having the skirt coated will help reduce friction on the cyl walls and improve mpg and breaking in the motor. Both very good things to consider when orderingpistons. It will increase the cost about $75-125 but worth it to some since it will also increase the longevity of the motor while helping to produce power and reduce noise.

Piston Manufactors:

Wiseco - these are actually rated for stock disp, my 9.25:1 83mm pistons come to 10.16:1 c/r when installed

RODS - see top of page.


Crank bearings
Main Bearings
Main Bolts or Studs (stronger and reuseable)
Head bolts or Studs (stronger and reuseable)
Flywheel bolts
Rear main seal
Headgasket - Stock for 81-82mm or ALT (NA 20v) 82.5-83.5
Oil pan silicone sealant
Front seal
Valve cover gasket set
Timing belt kit, tensioner at the min

It is not needed, but really advised to replace the oil pump also. It is only about $100 which is cheap insurance when spending $1000's into a new motor.


Not going to go into this since its more work, but is an option since the crankwith block are cheap and can be built and then dropped into the car instead of using the stock engine and have more downtime. All info can be found here http://forums.vwvortex.com/zerothread?id=2436326

USING A TDI ALH BLOCK 2.1L BUILD (95.5mm crank)

Again, not to many willing to go this route, so a link will be given. http://forums.vwvortex.com/zerothread?id=2483044


Complete build up and then some http://forums.vwvortex.com/zerothread?id=3335766
Also if you are a catalog kind of guy, eurospec makes engines with 2.0-2.2 with a selection of c/r's.


02-24-2009, 10:20 PM
well well well, you have been a busy little bee posting all this. kick ass find. didnt have time to read it all, but it gives me something to do on my lunch hour tomorrow

02-25-2009, 06:37 PM
does this go for the audi guys too?

02-28-2009, 01:17 AM
does this go for the audi guys too?i think it was more based off the audi 1.8t 225. being that its from audifreaks.com

03-02-2009, 02:19 AM
extremely helpful!!! thank you eliott~!

03-02-2009, 08:29 AM
I guess the term "big turbo" is relative :)

03-02-2009, 08:41 AM
I guess the term "big turbo" is relative :)

So a HTA35r isnt big enough for you? :-p

03-03-2009, 11:35 PM
Cincy's piecing together a GT35 setup :) (I'm a mod on there btw)